Register Preservation in Inline ASM Blocks

[dsimcha]

What is the rule on who is responsible for saving registers when inserting an
inline ASM block into the middle of a function?  For example:

void fun() {
    auto ptr = somePointer();
    asm {
        mov EAX, ptr;
        lock;
        inc [EAX];
    }
}

Is this acceptable (will the compiler do what it needs to do to deal with my
usage of EAX), or do I need to do something more like:

asm {
    push EAX;
    lock;
    inc [EAX];
    pop EAX;
}

, leaving EAX exactly as I found it?